A geologist interested in research involving the formation and exhumation of sedimentary basins. I have significant field-research experience in the documentation, collection and archiving of field data, stratigraphic analysis, modelling of basin thermal and crustal structures, geomorphic and lineament analysis–using satellite gravity and remote sensing data.
As part of my dissertation, I study an important yet poorly understood group of sedimentary basins referred to as IntraCONtinental Sags (ICONS). There is substantial value in constraining their geologic history both as the sedimentary rocks within them preserve long-term record of earth history and are host to natural resources including water and hydrocarbons. I focus on a Paleozoic-Mesozoic Basin in Eastern Africa that is almost completely exposed due to the Cenozoic uplift and rifting in the East African Rift System. The result include the publication of a new formation mechanism for the basin, and provide implications for basin analysis and exploration in such settings. I plan to continue and expand my research into both crustal and basin scale analysis of interior sedimentary basins, using both field and satellite data. These includes expanding on my recent exposure to neotectonics and exhumation studies through multidisciplinary approach that promotes the application of morphotectonic, and thermochronologic techniques. Supervisors: Mohamed Abdelsalam (PhD)
This work aimed at understanding the lithological controls on the SW-flowing segment of the Blue ... more This work aimed at understanding the lithological controls on the SW-flowing segment of the Blue Nile and its ~ 1500-m deep Nile Gorge in the NW Ethiopian Plateau. The gorge exposes a ~ 1100-m-thick Mesozoic sedimentary section overlain by ~ 400-m-thick Cenozoic flood basalt. This work found no significant controls of the river channel by local structure. A NW–SE geologic cross-section was constructed to measure the valley width, the normalized valley width, and the valley asymmetry as a function of depth at 20-m intervals. Additionally, the amount of incision through time was calculated at 1-Ma interval starting 30 Ma. The Blue Nile, during its incision on the NW Plateau, (1) maintains an increase in width of ~ 30 m per 1- m, except when it incised into the upper part of flood basalts (~ 50 m per 1-m depth), a lower part of the Mesozoic sedimentary section dominated by shale–mudstone and sandstone unit (~ 70 m per 1-m depth), and a lowermost unit of the sedimentary section dominated by sandstone unit (10 m per 1- m depth); (2) maintains a NW asymmetry except in the lowermost sandstone unit where it becomes either symmetrical or asymmetrical to the NW or SE; (3) incised for ~ 700- m through the flood basalt and the upper sedimentary section between 30 and 10 Ma, an additional ~ 200- m through the middle sedimentary section between 10 and 6 Ma, and an additional ~ 600- m through the lower sedimentary section between 6 Ma and present.
We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia using ge... more We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia using geologic field and gravity data. The depth to Moho and lithospheric structure beneath the basin was imaged using two-dimensional (2D) radially-averaged power spectral analysis, Lithoflex three-dimensional (3D) forward and inverse modeling, and 2D forward modeling of the Bouguer gravity anomalies. Previous studies proposed that the basin was formed as part of a multi-branched rift system related to the breakup of Gondwana. Our results show that the MSB: (1) is circular to elliptical in map view and saucer shaped in cross sectional view, (2) is filled with terrestrial and shallow marine sedi-mentary rocks, (3) does not significantly structurally control the sedimentation and the major faults are post-depositional, (4) is characterized by a concentric gravity minima, (5) is underlain by an unstretched crust (~40 km thick) and thicker lithosphere (~120 km thick). These features compare positively with a group of basins known as IntraCONtinental Sags (ICONS), especially those ICONS formed over accre-tionary orogenic terranes. Since the MSB is located above the Neoproterozoic accretionary orogenic terranes of the Arabian-Nubian Shield (ANS), we propose that the formation of the MSB to be related to cooling and thickening of a juvenile sub-continental lithospheric mantle beneath the ANS, which most probably provided negative buoyancy, and hence subsidence in the MSB, leading to its formation as an ICONS. The MSB could be used as an outcrop analog for information about the internal facies architecture of ICONS because it is completely exhumed due to tectonic uplift on the western flank of the Afar Depression.
We use morphotectonic analysis to study the tectonic uplift history of the southeastern Ethiopian... more We use morphotectonic analysis to study the tectonic uplift history of the southeastern Ethiopian Plateau (SEEP). Based on studies conducted on the Northwestern Ethiopian Plateau, steady-state and pulsed tectonic uplift models were proposed to explain the growth of the plateau since ~30 Ma. We test these two models for the largely unknown SEEP. We present the first quantitative morphotectonic study of the SEEP. First, in order to infer the spatial distribution of the tectonic uplift rates, we extract geomorphic proxies including normalized steepness index k sn , hypsometric integral HI, and chi integral χ from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation model (DEM). Second, we compare these rates with the thickness of flood basalt that we estimated from geological maps. Third, to constrain the timing of regional tectonic uplift, we develop a knickpoint celerity model. Fourth, we compare our results to those from the Northwestern Ethiopian Plateau to suggest a possible mechanism to explain regional tectonic uplift of the entire Ethiopian Plateau. We find an increase in tectonic uplift rates from the southeastern escarpments of the Afar Depression in the northeast to that of the Main Ethiopian Rift to the southwest. We identify three regional tectonic uplift events at ~11.7, ~6.5, and ~4.5 Ma recorded by the development of regionally distributed knickpoints. This is in good agreement with ages of tectonic uplift events reported from the Northwestern Ethiopian Plateau.
Soil formation occurs through numerous physical and chemical weathering processes acting to alter... more Soil formation occurs through numerous physical and chemical weathering processes acting to alter the parent rock on the Earth's surface. Samples of surface soils were collected over a range of elevations (2000–3600 m) from profiles directly overlying basaltic to more felsic parent rocks, over a region in NW Ethiopia. The soils were investigated to determine their chemical composition and X‑ray diffraction was used to identify and quantify individual mineral phases. The data set was ana‑ lyzed using non‑parametric statistics (Spearman's Rank and Mann‑Whitney U tests) to compare the soils forming over the two parent rocks. Principal component analysis (PCA) was used to identify the mineral alteration assemblage and formation during pedogenesis. The extent of alteration was quanti‑ fied using several chemical weathering indices (Chemical Index of Alteration = CIA; Chemical Index of Weathering = CIW), including an index calculated by multivariate analyses of the soil chemical composition data (weathering " W " index). Further to this we devised and tested a new weathering index (W min) using multivariate analysis of the soil mineralogy, to estimate the extent of weathering and physico‑chemical proprieties of the parent rock from which the soil formed. The soils present a fair to advanced stage of alteration, with abundant iron (Fe) oxides (up to 40 wt%) and phyllosilicates (up to 57 wt%), including kaolinite‑smectite (K‑S) mixed‑layer phases. The K‑S was composed of either 30–50% kaolinite or 94–98% kaolinite layers. Discrete kaolinite was also present. The bimodal K‑S mineralogical composition is likely due to two precursor phases: feldspar for the kaolinite‑rich K‑S and volcanic glass for the smectite‑rich K‑S. K‑S with intermediate composition (50–94% kaolinite) was rare, due to its instability. Statistical analysis showed significant differences between the chemical compositions of the soils developed on the two different parent volcanic composi‑ tions. The soils overlying the more felsic parent rocks were less altered than those overlying the flood basalt. When comparing the weathering indices calculated in this study, we conclude that while the CIA and CIW may be more readily determined, the W and W min indices can elucidate information on the composition of the original rock from which they formed. The W index is more sensitive to certain variables when compared with the newly derived mineralogical W min index; however the W min index takes into account mineral phases within the sample, which provides a more detailed interpretation of weathering rates than chemistry alone. In addition the W min index correlated with meteorological variables, such as elevation (and consequently temperature and precipitation), known to influence the degree of pedogenesis. The W min index can be used to enhance our understanding of the processes that occur during weathering processes to supplement information gained from traditional chemical weathering indices.
This work aimed at understanding the lithological controls on the SW-flowing segment of the Blue ... more This work aimed at understanding the lithological controls on the SW-flowing segment of the Blue Nile and its ~ 1500-m deep Nile Gorge in the NW Ethiopian Plateau. The gorge exposes a ~ 1100-m-thick Mesozoic sedimentary section overlain by ~ 400-m-thick Cenozoic flood basalt. This work found no significant controls of the river channel by local structure. A NW–SE geologic cross-section was constructed to measure the valley width, the normalized valley width, and the valley asymmetry as a function of depth at 20-m intervals. Additionally, the amount of incision through time was calculated at 1-Ma interval starting 30 Ma. The Blue Nile, during its incision on the NW Plateau, (1) maintains an increase in width of ~ 30 m per 1- m, except when it incised into the upper part of flood basalts (~ 50 m per 1-m depth), a lower part of the Mesozoic sedimentary section dominated by shale–mudstone and sandstone unit (~ 70 m per 1-m depth), and a lowermost unit of the sedimentary section dominated by sandstone unit (10 m per 1- m depth); (2) maintains a NW asymmetry except in the lowermost sandstone unit where it becomes either symmetrical or asymmetrical to the NW or SE; (3) incised for ~ 700- m through the flood basalt and the upper sedimentary section between 30 and 10 Ma, an additional ~ 200- m through the middle sedimentary section between 10 and 6 Ma, and an additional ~ 600- m through the lower sedimentary section between 6 Ma and present.
We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia using ge... more We investigated the evolution of the Mekele Sedimentary Basin (MSB) in northern Ethiopia using geologic field and gravity data. The depth to Moho and lithospheric structure beneath the basin was imaged using two-dimensional (2D) radially-averaged power spectral analysis, Lithoflex three-dimensional (3D) forward and inverse modeling, and 2D forward modeling of the Bouguer gravity anomalies. Previous studies proposed that the basin was formed as part of a multi-branched rift system related to the breakup of Gondwana. Our results show that the MSB: (1) is circular to elliptical in map view and saucer shaped in cross sectional view, (2) is filled with terrestrial and shallow marine sedi-mentary rocks, (3) does not significantly structurally control the sedimentation and the major faults are post-depositional, (4) is characterized by a concentric gravity minima, (5) is underlain by an unstretched crust (~40 km thick) and thicker lithosphere (~120 km thick). These features compare positively with a group of basins known as IntraCONtinental Sags (ICONS), especially those ICONS formed over accre-tionary orogenic terranes. Since the MSB is located above the Neoproterozoic accretionary orogenic terranes of the Arabian-Nubian Shield (ANS), we propose that the formation of the MSB to be related to cooling and thickening of a juvenile sub-continental lithospheric mantle beneath the ANS, which most probably provided negative buoyancy, and hence subsidence in the MSB, leading to its formation as an ICONS. The MSB could be used as an outcrop analog for information about the internal facies architecture of ICONS because it is completely exhumed due to tectonic uplift on the western flank of the Afar Depression.
We use morphotectonic analysis to study the tectonic uplift history of the southeastern Ethiopian... more We use morphotectonic analysis to study the tectonic uplift history of the southeastern Ethiopian Plateau (SEEP). Based on studies conducted on the Northwestern Ethiopian Plateau, steady-state and pulsed tectonic uplift models were proposed to explain the growth of the plateau since ~30 Ma. We test these two models for the largely unknown SEEP. We present the first quantitative morphotectonic study of the SEEP. First, in order to infer the spatial distribution of the tectonic uplift rates, we extract geomorphic proxies including normalized steepness index k sn , hypsometric integral HI, and chi integral χ from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation model (DEM). Second, we compare these rates with the thickness of flood basalt that we estimated from geological maps. Third, to constrain the timing of regional tectonic uplift, we develop a knickpoint celerity model. Fourth, we compare our results to those from the Northwestern Ethiopian Plateau to suggest a possible mechanism to explain regional tectonic uplift of the entire Ethiopian Plateau. We find an increase in tectonic uplift rates from the southeastern escarpments of the Afar Depression in the northeast to that of the Main Ethiopian Rift to the southwest. We identify three regional tectonic uplift events at ~11.7, ~6.5, and ~4.5 Ma recorded by the development of regionally distributed knickpoints. This is in good agreement with ages of tectonic uplift events reported from the Northwestern Ethiopian Plateau.
Soil formation occurs through numerous physical and chemical weathering processes acting to alter... more Soil formation occurs through numerous physical and chemical weathering processes acting to alter the parent rock on the Earth's surface. Samples of surface soils were collected over a range of elevations (2000–3600 m) from profiles directly overlying basaltic to more felsic parent rocks, over a region in NW Ethiopia. The soils were investigated to determine their chemical composition and X‑ray diffraction was used to identify and quantify individual mineral phases. The data set was ana‑ lyzed using non‑parametric statistics (Spearman's Rank and Mann‑Whitney U tests) to compare the soils forming over the two parent rocks. Principal component analysis (PCA) was used to identify the mineral alteration assemblage and formation during pedogenesis. The extent of alteration was quanti‑ fied using several chemical weathering indices (Chemical Index of Alteration = CIA; Chemical Index of Weathering = CIW), including an index calculated by multivariate analyses of the soil chemical composition data (weathering " W " index). Further to this we devised and tested a new weathering index (W min) using multivariate analysis of the soil mineralogy, to estimate the extent of weathering and physico‑chemical proprieties of the parent rock from which the soil formed. The soils present a fair to advanced stage of alteration, with abundant iron (Fe) oxides (up to 40 wt%) and phyllosilicates (up to 57 wt%), including kaolinite‑smectite (K‑S) mixed‑layer phases. The K‑S was composed of either 30–50% kaolinite or 94–98% kaolinite layers. Discrete kaolinite was also present. The bimodal K‑S mineralogical composition is likely due to two precursor phases: feldspar for the kaolinite‑rich K‑S and volcanic glass for the smectite‑rich K‑S. K‑S with intermediate composition (50–94% kaolinite) was rare, due to its instability. Statistical analysis showed significant differences between the chemical compositions of the soils developed on the two different parent volcanic composi‑ tions. The soils overlying the more felsic parent rocks were less altered than those overlying the flood basalt. When comparing the weathering indices calculated in this study, we conclude that while the CIA and CIW may be more readily determined, the W and W min indices can elucidate information on the composition of the original rock from which they formed. The W index is more sensitive to certain variables when compared with the newly derived mineralogical W min index; however the W min index takes into account mineral phases within the sample, which provides a more detailed interpretation of weathering rates than chemistry alone. In addition the W min index correlated with meteorological variables, such as elevation (and consequently temperature and precipitation), known to influence the degree of pedogenesis. The W min index can be used to enhance our understanding of the processes that occur during weathering processes to supplement information gained from traditional chemical weathering indices.
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